Internal exhaust seal for electric lamps and similar devices



June 21, 1949. P. o. CARTUN INTERNAL EXHAUST SEAL FOR ELECTRIC 'lnvenTorO. Cor-Tun,

. His ATTor'ney- LAMPS AND SIMILAR DEVICES Filed Nov.

.IIIIIIILIII Patented June 21, 1949 INTERNAL EXHAUST SEAL FOR ELECTRICLAMPS AND SIMILAR DEVICES Paul 4). Carton, Cleveland Heights, Ohio,assignor to General Electric Company, a corporation of New YorkApplication November 9, 1946, Serial No. 708,919

2 Claims.

This invention relates to seals for envelope openings or connectionssuch as the exhaust tubes of incandescent lamps and electric dischargedevices. The exhaust tubes of such devices are customarily closed andsealed outside the envelope, leaving an external tip that usuallyprojects outward from the portion of the envelope to which the exhausttube is attached.

Such an external tip or seal being sometimes undesirable, it is anobject of my invention to provide a novel means of sealing which can beperformed entirely inside the envelope, resulting in a seal that iswholly internal. Various novel features and advantages of the inventionwill appear from the following description of species thereof and fromthe drawing.

In the drawing, Fig. 1 is an elevation of one end of a lamp envelope,illustrating the sealing of its exhaust connection in accordance with myinvention; Fig. 2 is a fragmentary View showing the completed seal; Fig.3 is a view similar to Fig. 1 illustrating a modified form of thesealing structure; Figs. 4 and 5 are similar views illustrating theapplication of my invention in connection with envelopes of other types;and Fig. 6 is a fragmentary view of still another modification.

Fig. 1 illustrates the application of my invention to an electric lampof one ordinary incandescent type such as shown in U. S. Patents Nos.1,590,164 to Harrington et al. and 2,042,540 to Manders, although theinvention is equally applicable to other types of lamps and electricaldevices. In this case the end of the envelope l is closed by a flaredglass stem 2 with leading-in wires 3, 3 sealed through a seal 4 at itsupper or inner end and extending inward into the envelope to which thestem is sealed at 5. The filament connected between the current leads 3,3 is not shown, nor any auxiliary supporting means for this filament.The seal 4 is shown as of an unpressed fused type such as illustrated inU. S. Patent No. 2,128,173 to White.

A small glass tube 6 generally corresponding to the exhaust connectionin common use heretofore is sealed and open through the stem seal 4 andprojects inward beyond this seal 4, as shown. The tube 6 is kept open byany suitable means while the end of stem tube 2 is being fused andsealed around and to it, as by a mandrel or pin inside said tube 6, asshown, for example, in U. S. Patent No. 1,491,436 to Strickland. Afterthe mount including stem 2 has been sealed into the envelope I, theconnection afforded by the tube 6 may be used for exhausting air fromthe bulb,

2 or for filling the envelope with gas or other atmosphere, or both.Following this, it is desired to close and seal off the tube 6.

For this purpose, a thin disc-like sealing member or closure 7 is shownin Fig. 1 against the inner end or mouth 8 of the tube 6, preferably adisc of sheet metal like chrome iron such as that known as Allegheny 55which has the property of being wet by fused glass and sealing andadhering strongly thereto and has a coelhcient of expansion similar tothat of the glass. This member I is held in position opposite the mouth8 by a support member 9 suitably attached to the lamp structure, leavingthe mouth of the tube initially open for use, and capable of pressingthe disc 1 against the said mouth of the tube to seal it thereto whenthe parts are heated. As shown, the open mouth end 8 of the tube 6 hasan angular peripheral configuration, in this case biased and sloped awayfrom the disc 1, which merely rests against the high side of the mouth.The support 9 preferably consists of a spring of fine wire such asmolybdenum which retains its springiness under heat, and is looped orcoiled in the general plane of the lamp axis, with one end secured(preferably welded) to the member I and the other end welded to a lead3.

To close the mouth 8, after the lamp has been evacuated (and gas filled,if desired) by connecting the lower end of tube 6 to an exhaust pump,the disc 1 is heated by any suitable means, preferably an induction coill0 temporarily placed around the envelope. The mouth 8 being also heatedby radiation and conduction from the disc 1, it is fused and sealed tothe said disc 1 which is pressed against it by the spring 9. Thus theconnection 6 is closed and permanently sealed, the completed seal beingshown in Fig. 2, after which the tube 6 may be severed at the line I I.The support member 9 may be constituted of a bimetallic strip in whichcase it is pressed against the mouth 8 upon expansion due to the heatingof the parts by coil Ill.

The modification shown in Fig. 3 is the same as that shown in Fig. 1except that the supporting member 9a for the disc 1 is in the form of ahelical spring arranged concentric with the axis of the envelope I andthe tube 6 to press the disc 1 against the said tube 6.

Fig. 4 illustrates the application of my invention to a lamp envelope lbwhose end wall is formed of an embossed sheet metal disc l2 that may beof chrome iron, as shown in my U. S. Patent No. 2,048,491. Here theexhaust tube 6b is shown as sealed by fusion to the inner side of thedisc I2 around a. central hole I 3 in this disc, and the coiled springsupport 9b for the sealing member lb is bent over and welded to the discl2 near its edge.

Fig. 5 illustrates the application of the invention to a tubular lampsuch as shown in my Patent No. 2,082,616, in a manner mainly similar tothat shown in Fig. 4. The principal difference is that the springsupport He for the sealing member is bent in a reverse curve instead ofinto a coil,- and is welded to a wire l4 forming part of the filamentsupporting structure extending from end to end of the lamp. Instead of amere spring, the member 90 may be a bimetallic strip so that,

upon heating, it firmly presses the disc Ic againstthe tube 60 extendingfrom the metal end disc 1 I0.

In the modification of Fig. 1 shown in Fig. 6, the angular peripheralconfiguration of the mouth of the tube 6d consists of a notch or notchesin the form of one or more V-shaped openings 8d. The closure disc 1d iscarried by one end of a bimetallic strip 9d the other end of which issecured to a lead 31) and which, upon being heated by the disc id, isdeformed to press the said disc firmly against the mouth of the tube 6dto seal it thereto, the finished seal being substantially the same asshown in Fig. 2.

metal adapted to fuse hermetically tight to glass, and a. bimetallicsupport member carrying said disc and holding it adjacent the mouth ofsaid tube in a position to leave the mouth open to the interior of theenvelope and constructed and arranged to press the said disc against thesaid mouth of the tube to seal it thereto when the parts are heated.

2. In an envelope having a reentrant glass exhaust tube extendingthereinto, the mouth of said tube having an angular peripheralconfiguration, a sealing structure in said envelope comprising a closuredisc of metal adapted to fuse hermetically tight to glass, and abimetallic support member carrying said disc and holding it against themouth of said tube in a position to leave the mouth open to the interiorof the envelope and constructed and arranged to press the said discagainst the said mouth of the tube to seal it thereto when the parts areheated.

PAUL O. CARTUN.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 2,125,316 Ronci Aug. 2, 1938FOREIGN PATENTS Number Country Date 111,419 Australia Aug. 28, 1940701,250 Germany Jan. 11, 1941

